Synthesis of icariin in tobacco leaf by overexpression of a glucosyltransferase gene from Epimedium sagittatum

Epimedium plants are globally known for gardening and medicinal purposes. They are a potential resource of biologically active pharmaceutical compounds that can be used to treat various diseases. Among these compounds, icariin, a glycosylated flavonoid, has significant anti-tumor, bone growth, and neuroprotective effects; however, its biosynthetic pathway remains unknown. In this study, icariin accumulation during the development of leaves of Epimedium sagittatum was investigated. We identified a glycosyltransferase (Epimedium sagittatum glycosyltransferase, EsGT1) gene from this species using transcriptional analysis. Heterogeneously expressed EsGT1 protein transferred icariside II to icariin at the 7-OH site and its catalytic function was validated in vivo by the overexpression of the gene. In the recombinant protein assay, EsGT1 was also active in the glycosylation of kaempferol, an intermediate product of icariin. These results characterized the final step of glycosyltransferase in icariin synthesis and suggested an economical and efficient alternative source of icariin using a tobacco biotechnological method.